Induction-softened thermoplastic shims

ABSTRACT

A shim assembly includes a shim material configured to be positioned between a first component and a second component. A wire is in contact with the shim material. The wire is configured to heat the shim material to above a predetermined temperature, and the shim material becomes moldable above the predetermined temperature such that the shim material is able to conform to the first component and the second component.

TECHNICAL FIELD

The present teachings relate to the field of shims that fill voidsbetween two components and, more particularly, to induction-softenedthermoplastic shims.

BACKGROUND

The assembly of large structures may be hampered by dimensionalmismatching, which may create a void at the interface between twocomponents. This is especially problematic when one or more bag-sidesurfaces are at the interface. Shims are one common way to fill suchvoids. One common type of shim is the liquid shim, which includes anepoxy material. After the liquid shim is applied, the components areassembled with either temporary fasteners (e.g., clekos), or with thefinal fasteners partially torqued. Once the liquid shim sets (e.g.,dries), the final fasteners are fully torqued. The liquid shim may takea day or more to set. What is needed is an improved shim that sets morequickly.

SUMMARY

The following presents a simplified summary in order to provide a basicunderstanding of some aspects of the present teachings. This summary isnot an extensive overview, nor is it intended to identify key orcritical elements of the present teachings, nor to delineate the scopeof the disclosure. Rather, its primary purpose is merely to present oneor more concepts in simplified form as a prelude to the detaileddescription presented later.

A shim assembly is disclosed. The shim assembly includes a shim materialconfigured to be positioned between a first component and a secondcomponent. A wire is in contact with the shim material. The wire isconfigured to heat the shim material to above a predeterminedtemperature, and the shim material becomes moldable above thepredetermined temperature such that the shim material is able to conformto the first component and the second component.

A method for assembling a first component and a second component is alsodisclosed. The method includes embedding a wire at least partiallywithin a shim material. The shim material is then placed at leastpartially between the first and second components. The first and secondcomponents are then together using a first coupling device. Anelectrical current is then induced in the wire. The electrical currentcauses the wire to heat the shim material to above a predeterminedtemperature, and the shim material becomes moldable above thepredetermined temperature such that the shim material is able to conformto the first component and the second component.

The features, functions, and advantages that have been discussed can beachieved independently in various implementations or may be combined inyet other implementations further details of which can be seen withreference to the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate the present teachings andtogether with the description, serve to explain the principles of thedisclosure. In the figures:

FIG. 1A depicts a schematic view of two components having a shimmaterial positioned therebetween.

FIG. 1B depicts a schematic view of the two components having the shimmaterial positioned therebetween where the two components are coupledtogether with a cleko.

FIG. 2 depicts a flowchart of a method for assembling the twocomponents.

FIG. 3 depicts a schematic view of an induction coil positionedproximate to the shim material.

FIG. 4 depicts a schematic view of the shim material softening, allowingthe two components to move closer together.

FIG. 5 depicts a schematic view of the induction coil positioned betweenthe two components.

FIG. 6 depicts a side view of a first wire having a second wire wrappedhelically around it.

FIG. 7 depicts a perspective view of a plurality of the first wiressubstantially parallel to one another where each of the first wires hasa second wire wrapped helically around it.

FIG. 8 depicts a side cross-sectional view of the wires from FIG. 7positioned between two layers of the shim material.

It should be noted that some details of the Figures have been simplifiedand are drawn to facilitate understanding of the present teachingsrather than to maintain strict structural accuracy, detail, and scale.

DETAILED DESCRIPTION

Reference will now be made in detail to examples of the presentteachings, which are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts.

The embodiments described herein provide an induction-softenedthermoplastic shim. For example, FIG. 1A depicts a schematic view of twocomponents 110, 120 having a shim material 130 positioned therebetween.In at least one embodiment, the components 110, 120 may be part of anaircraft, such as an airplane, a helicopter, an unmanned aerial vehicle(“UAV”), or the like. In one example, the first component 110 may be orinclude a rib, and the second component 120 may be or include wing skinsto spars. The components 110, 120 may be made from a composite materialor a metallic material. In one example, the composite material may be acarbon, fiberglass, or other fiber-reinforced plastic that cures at atemperature from about 300° F. to about 400° F. or about 325° F. toabout 375° F. (e.g., about 350° F.). In another example, the metallicmaterial may be titanium.

The components 110, 120 may have inconsistent tolerances such that thecomponents 110, 120 may not be flush with one another when coupledtogether. In other words, one or more voids may be present between thecomponents 110, 120 when the components 110, 120 are coupled together.In one example, the voids may be present in the bag-side surfaces of oneor both of the components 110, 120.

The shim material 130 may be positioned between the two components 110,120 and configured to fill the voids. The shim material 130 may be madefrom a polymer such as a fiber-reinforced plastic. More particularly,the shim material 130 may be made from a thermoplastic and/or epoxymaterial that softens and becomes pliable and/or moldable above apredetermined temperature and hardens/solidifies below the predeterminedtemperature. For example, the shim material 130 may be or include apolycarbonate material having a predetermined temperature from about250° F. to about 320° F., about 265° F. to about 305° F., or about 280°F. to about 290° F. The predetermined temperature at which the shimmaterial 130 becomes pliable and/or moldable may be less than thetemperature at which the components 110, 120 cure.

One illustrative polycarbonate material that may be used is TARFLON®,which has a yield strength of up to 19 KSI and a mold temperature fromabout 150° F. to about 300° F. The polycarbonate material may alsoinclude flame-proof additives. In addition to polycarbonate materials,other plastics may also be used depending on the location, strengthrequirements, chemical resistance requirements, UV resistance, and thelike. Such plastics may be or include acrylonitrile butadiene styrene(“ABS”), polyvinyl chloride (“PVC”), polystyrene (“PS”),poly(p-phenylene oxide) (“PPO”), poly(methyl methacrylate), polyethyleneterephthalate (“PET”), polyamide, or the like.

In at least one embodiment, a mesh material 140 may be positioned atleast partially within (e.g., embedded within) or around the shimmaterial 130. The mesh material 140 may be or include fiberglass, carbongraphite, quartz, boron, other fiber materials, flame-retardants, or acombination there. The mesh material 140 may prevent the shim material130 from extruding/creeping when compressed by the two components 110,120.

One or more wires (one is shown: 150) may be in contact with the shimmaterial 130. For example, the wire 150 may be positioned at leastpartially within (e.g., embedded within) the shim material 130.Together, the shim material 130, the mesh material 140, the wire 150, ora combination thereof may form a shim assembly that may be positionedbetween the components 110, 120.

In one embodiment, the wire 150 may be in a substantially serpentine(e.g., S-shaped) pattern in a single plane. In another embodiment, thewire 150 may be wrapped around the first component 110 or the secondcomponent 120 in a substantially helical pattern. The wire 150 may be orinclude an induction susceptor wire that is made from a ferromagneticmaterial. More particularly, the wire 150 may include iron, nickel,cobalt, manganese, chromium, or a combination thereof. For example, thewire 150 may include an alloy containing about 34 wt % nickel and about66 wt % iron, which may have a smart leveling temperature from about300° F. to about 340° F. The smart leveling temperature is thetemperature where the wire 150 becomes substantially non-magnetic. Thistemperature is typically below the established Curie temperature of thewire 150. In another example, the wire 150 may include an alloycontaining about 32 wt % nickel and about 68 wt % iron, which may have asmart leveling temperature from about 240° F. to about 300° F. The wire150 may have a cross-sectional length (e.g., diameter) from about 50micrometers (μm) to about 500 μm, about 100 μM to about 400 μM, or about150 μM to about 350 μm.

The wire 150 may be configured to heat to a predetermined temperature(e.g., Curie temperature) when exposed to an electromagnetic field. Thewire 150 may not be heated efficiently above the smart levelingtemperature. The smart leveling temperature of the wire 150 may begreater than or equal to the temperature at which the shim material 130becomes pliable and/or moldable and less than the temperature at whichthe components 110, 120 cure so as to not damage the components 110,120. For example, the smart leveling temperature of the wire 150 may befrom about 260° F. to about 340° F., about 275° F. to about 325° F., orabout 290° F. to about 310° F.

FIG. 2 depicts a flowchart of a method 200 for assembling first andsecond components 110, 120. Various stages of the method 200 areillustrated in FIGS. 1, 3, and 4. The method 200 may begin by embeddingthe wire 150 at least partially into the shim material 130, as at 202.This is shown in FIG. 1A. The method 200 may also include placing theshim material 130 (with the wire 150 embedded therein) between the twocomponents 110, 120, as at 204. This is also shown in FIG. 1A.

The method 200 may also include coupling the two components 110, 120together using one or more first coupling devices (two are shown: 160),as at 206. This is also shown in FIG. 1A. More particularly, the firstcoupling devices 160 may inserted into holes that are formed (e.g.,drilled) through the first component 110, the second component 120, theshim material 130, the mesh material 140, the wire 150, or a combinationthereof. The first coupling devices 160 may be or include a nut, a bolt,a screw, an adhesive, a band, a strap, or a combination thereof. Inanother embodiment, the first coupling device 160 may be or include acleko, as shown in FIG. 1B.

The method 200 may also include torqueing the first coupling devices 160to an initial level, as at 208. The initial level may be less than afinal torque level. This may provide a preloading.

The method 200 may also include inducing an electrical current in thewire 150, as at 210. The electrical current may be induced when the shimmaterial 130 (with the wire 150 embedded therein) is between the twocomponents 110, 120, and the two components 110, 120 are coupledtogether. In at least one embodiment, the current may be induced bymaking the wire 150 part of a closed circuit (e.g., physicallyconnecting an end of the wire 150 to a power source). In anotherembodiment, the current may be induced wirelessly. For example, aninduction coil 170 may be positioned proximate to the wire 150. This isshown in FIG. 3. When the induction coil 170 is positioned external tothe composite material (e.g., the first component 110 and/or the secondcomponent 120), as shown in FIG. 3, the induction coil 170 may besupplied with an alternating current (“AC”) having a frequency fromabout 10 kHz to about 30 kHz or about 15 kHz to about 25 kHz to avoidunwanted heating of the components 110, 120. When the induction coil 170is positioned internal to the composite material (e.g., the firstcomponent 110 and/or the second component 120), as shown in FIG. 5, theinduction coil 170 may be supplied with an alternating current having afrequency from about 80 kHz to about 500 kHz or about 150 kHz to about300 kHz because the field does not need to penetrate the compositematerial to heat the wire 150. In response to the current, the inductioncoil 170 may generate an electromagnetic field. The electromagneticfield may be substantially parallel to a central longitudinal axisthrough the wire 150. In another embodiment, the electromagnetic fieldmay be substantially perpendicular to the central longitudinal axisthrough the wire 150.

The electromagnetic field may cause the wire 150 to increase intemperature. More particularly, the wire 150 may increase in temperatureuntil the wire 150 reaches the smart leveling temperature, at whichpoint the temperature of the wire 150 may remain substantially constantat the smart leveling temperature as long as the electromagnetic fieldis present. The heat generated by the wire 150 may be transferred to thesurrounding shim material 130. As discussed above, when the shimmaterial 130 reaches the predetermined temperature, the shim material130 softens and becomes pliable and/or moldable. When the shim material130 softens and becomes pliable and/or moldable, the preloading(discussed above) may cause the shim material 130 to fill the void(s) byconforming to the surfaces of the components 110, 120.

The method 200 may also include torqueing the first coupling devices 160to a final level that is greater than the initial level, as at 212. Thisis shown in FIG. 4. In at least one embodiment, the first couplingdevices 160 may be torqued to the final level when the shim material 130is above the predetermined temperature. In another embodiment, the firstcoupling devices 160 may be torqued to the final level once the currentis no longer induced (e.g., a few minutes after the current is reducedor cut off) and the shim material 130 falls back below the predeterminedtemperature. In at least one embodiment, rather than torqueing the firstcoupling devices 160 to the final level, the first coupling devices 160may be removed, and one or more second coupling devices may be insertedand torqued to the final level.

Once the method 200 is complete, the induction coil 170 may be movedaway from the components 110, 120, the shim material 130, and the wire140. The wire 140, however, may remain positioned within the shimmaterial 130 and between the components 110, 120.

FIG. 5 depicts a schematic view of the induction coil 170 positionedbetween the two components 110, 120. The induction coil 170 may becoupled to or integral with the shim material 130 and/or the wire 140.In at least one embodiment, the wire 140 and/or the induction coil 170may remain positioned between the two components 110, 120 as the twocomponents 110, 120 are moved closer together (as in step 210 above). Inanother embodiment, the wire 140 and/or the induction coil 170 may beremoved from between the two components 110, 120 before the twocomponents 110, 120 are moved closer together (as in step 210 above).

FIG. 6 depicts a side view of a first wire 610 having a second wire 620wrapped helically around it, and FIG. 7 depicts a perspective view of aplurality of the first wires 610 substantially parallel to one anotherwhere each of the first wires 610 has a second wire 620 wrappedhelically around it. The first wire 610 may be or include a copper wire(e.g., Litz wire) having a plurality of strands. The first wire 610 mayserve as the induction coil 170 described above. The first wire 610 mayprovide low electrical resistance at high frequencies. When electricalcurrent flows through the first wire 610, a magnetic field is generatedthat is parallel to the axis of the first wire 610.

The second wire 620 may be or include a smart susceptor wire, similar tothe wire 150 described above. The first wire 610 with the second wire620 wrapped therearound may form a heater ribbon. The heater ribbon mayuse a continuous electrical path despite holes in the heater ribbon.Thus, the first wires 610 may be diverted around the holes in the heaterribbon. The first and second wires 610, 620 may be encased in ahigh-temperature layer to create a heater strip of known thickness.

FIG. 8 depicts a side cross-sectional view of the wires 610, 620 fromFIG. 7. The wires 610 and/or 620 may be embedded within a material 140,which may be another polymer material with a melting temperature that ishigher than the shim material 130. The material 140 with the wires 610,620 therein may be placed between two layers of the shim material 130.The shim material 130 may then be placed between the two components 110,120. The magnetic field generated by the first wires 610 may inductivelyheat the second wires 620, which may cause the shim material 130 tosoften. As described above, when the shim material 130 softens andbecomes pliable and/or moldable, the preloading may cause the shimmaterial 130 to fill the void(s) by conforming to the surfaces of thecomponents 110, 120. In at least one embodiment, the first and secondwires 610, 620 and the material 140 may be removed after the shimmaterial 130 fills the voids.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the present teachings are approximations, thenumerical values set forth in the specific examples are reported asprecisely as possible. Any numerical value, however, inherently containscertain errors necessarily resulting from the standard deviation foundin their respective testing measurements. Moreover, all ranges disclosedherein are to be understood to encompass any and all sub-ranges subsumedtherein. For example, a range of “less than 10” can include any and allsub-ranges between (and including) the minimum value of zero and themaximum value of 10, that is, any and all sub-ranges having a minimumvalue of equal to or greater than zero and a maximum value of equal toor less than 10, e.g., 1 to 5. In certain cases, the numerical values asstated for the parameter can take on negative values. In this case, theexample value of range stated as “less than 10” can assume negativevalues, e.g. −1, −2, −3, −10, −20, −30, etc.

While the present teachings have been illustrated with respect to one ormore implementations, alterations and/or modifications can be made tothe illustrated examples without departing from the spirit and scope ofthe appended claims. It will be appreciated that structural componentsand/or processing stages can be added or existing structural componentsand/or processing stages can be removed or modified. Furthermore, to theextent that the terms “including,” “includes,” “having,” “has,” “with,”or variants thereof are used in either the detailed description and theclaims, such terms are intended to be inclusive in a manner similar tothe term “comprising.” The term “at least one of” is used to mean one ormore of the listed items can be selected. Further, in the discussion andclaims herein, the term “on” used with respect to two materials, one“on” the other, means at least some contact between the materials, while“over” means the materials are in proximity, but possibly with one ormore additional intervening materials such that contact is possible butnot required. Neither “on” nor “over” implies any directionality as usedherein. The term “about” indicates that the value listed may be somewhataltered, as long as the alteration does not result in nonconformance ofthe process or structure to the present teachings. The presentdisclosure provides specific implementations without being exhaustive,and other implementations of the present teachings may be apparent tothose skilled in the art from consideration of the specification andpractice of the disclosure herein. It is intended that the specificationand examples be considered as exemplary only, with a true scope andspirit of the present teachings being indicated by the following claims.

1. A shim assembly, comprising: a shim material configured to bepositioned between a first component and a second component; a wire incontact with the shim material, wherein the wire is configured to heatthe shim material to above a predetermined temperature, and wherein theshim material becomes moldable above the predetermined temperature suchthat the shim material is able to conform to the first component and thesecond component.
 2. The shim assembly of claim 1, wherein the wire isembedded in the shim material.
 3. The shim assembly of claim 2, whereinthe wire heats to a leveling temperature that is greater than thepredetermined temperature at which the shim material becomes moldable,and wherein the Curie temperature is less than a temperature at whichthe first component and the second component cure.
 4. The shim assemblyof claim 3, wherein the predetermined temperature is from about 250° F.to about 320° F.
 5. The shim assembly of claim 3, wherein the levelingtemperature is from about 260° F. to about 340° F.
 6. The shim assemblyof claim 3, wherein the wire heats the shim material in response tobeing exposed to an electromagnetic field generated by an inductioncoil.
 7. The shim assembly of claim 3, wherein the shim materialcomprises a thermoplastic material.
 8. The shim assembly of claim 7,wherein the wire is made from a ferromagnetic material.
 9. The shimassembly of claim 8, wherein the wire is made from iron, nickel, cobalt,manganese, chromium, or a combination thereof.
 10. The shim assembly ofclaim 9, further comprising a fiberglass mesh material that is embeddedat least partially within the shim material.
 11. A method for assemblinga first component and a second component, comprising: embedding a wireat least partially within a shim material; placing the shim material atleast partially between the first and second components; coupling thefirst and second components together using a first coupling device; andinducing an electrical current in the wire, wherein the electricalcurrent causes the wire to heat the shim material to above apredetermined temperature, wherein the shim material becomes moldableabove the predetermined temperature such that the shim material is ableto conform to the first component and the second component.
 12. Themethod of claim 11, wherein the electrical current is induced using aninduction coil.
 13. The method of claim 12, wherein the induction coilis positioned on an opposing side of the first component or the secondcomponent from the shim material.
 14. The method of claim 12, whereinthe induction coil is positioned between the first and secondcomponents.
 15. The method of claim 12, wherein the induction coil iscoupled to or integral with the wire.
 16. The method of claim 11,further comprising torqueing the first coupling device to an initiallevel before inducing the electrical current.
 17. The method of claim16, further comprising torqueing the first coupling device to a finallevel after the shim material exceeds the predetermined temperature. 18.The method of claim 17, wherein the first coupling device is torqued tothe final level when the shim material is above the predeterminedtemperature.
 19. The method of claim 17, wherein the first couplingdevice is torqued to the final level after the shim material cools tobelow the predetermined temperature.
 20. The method of claim 16, furthercomprising: removing the first coupling device after the shim materialexceeds the predetermined temperature; and inserting and torqueing asecond coupling device to a final level that is greater than the initiallevel.